feat(fs): add caching option for lv_fs-read (#2979)

BREAKING CHANGE:
The `LV_FS_...` related configs needs to be updated.

Co-authored-by: Gabor Kiss-Vamosi <kisvegabor@gmail.com>

examples/libs/bmp/lv_example_bmp_1.c

@@ -9,7 +9,11 @@ void lv_example_bmp_1(void)
     lv_obj_t * img = lv_img_create(lv_scr_act());
     /* Assuming a File system is attached to letter 'A'
      * E.g. set LV_USE_FS_STDIO 'A' in lv_conf.h */
+#if LV_COLOR_DEPTH == 32
     lv_img_set_src(img, "A:lvgl/examples/libs/bmp/example_32bit.bmp");
+#elif LV_COLOR_DEPTH == 16
+    lv_img_set_src(img, "A:lvgl/examples/libs/bmp/example_16bit.bmp");
+#endif
     lv_obj_center(img);
 
 }